The present invention relates to an apparatus for pest control; and to the use of said apparatus for pest control.
A number of the more than 3000 species of tephritid fruit flies, in particular those of the genera Ceratitis, Dacus, Bactrocera and Rhagoletis, are important horticultural pests. The insects lay their eggs into mostly species-specific host plants after which many of the species are named (e. g. olives for Bactrocera oleae, squashes and pumpkins for B. cucurbitae, etc.), and the hatching larvae can cause extensive feeding damage, in particular by their often marked preference for either vulnerable parts of their host plant such as flowers (anthophagy) or the parts of the host plants intended to be marketed, such as fruits (carpophagy). Control of these pests, which, when occurring in larger amounts, may totally destroy the local harvest, is thus highly desirable but complicated by the fact that only about a third of the tephritid species described so far act as pests, whereas the remainder includes some important ecological regulators, such as species whose host plants are themselves agricultural pests.
Selective control of tephritid pests, as of many other insect pests, has exploited these insects' use of species-specific pheromones during mating. By using such pheromones, which are generally produced by the females and hence act as powerful attractants to males of the same species, it is possible to lure the male specimens of the species of interest into traps comprising a small amount of a contact pesticide sufficient for destroying them (“attract and kill” strategy). This general approach offers a number of advantages over more conventional applications of pesticides: Only a limited amount of the pesticide is required, which makes pest control cheaper, avoids ecological problems and reduces the health hazard to workers. Moreover, it is possible to selectively target species of interest, as the attractant can be selected to ensure that non-target species will not be lured into the traps.
In its simplest form, a pheromone-baited trap consists of an object that is freely accessible to the pests and comprises both a pheromone and a contact pesticide, such as the Amulet C-L Fruit Fly Station which comprises Cue-lure (=4-[p-hydroxyphenyl]-2-butanone acetate) as a pheromone specific for the horticultural pest Bactrocera tryoni (Queensland fruit fly) and fipronil as pesticide. However, these stations are suboptimal in that
rainwater may leach the contents from the stations;
the release of the contents may also contaminate the horticultural products which they are intended to protect; and
in or close to residential areas, people, in particular children, and pets might inadvertently come into contact and thus be exposed to fipronil.
These drawbacks may be overcome by placing the station in an enclosing shell or container which allows the target insects to easily access the stations while at the same time affording protection from rainwater and spatially locking out humans and larger animals, thereby forming a more selective trap for the target pests. A variety of such traps, e. g. for fruit flies, are commercially available for controlling and eradicating tephritid pests, such as Bucket traps, Steiner traps, McPhail traps, FT Wafer traps, modified soda bottle traps, modified milk jug traps, etc. They all share the common feature of “trapping” the pest, i. e., the insect lured into the trap will be killed inside, and its carcass will remain there until taken out or naturally decomposed. This offers the benefit of being able to monitor and record populations, capture being the primary purpose of these traps.
However, the disadvantage of this approach is that it is exclusively those individuals displaying active seeking behaviour which are killed. These are the males of the species of interest, which have to be considered less important for the stability and reproductive potential of the population than the females, in particular in insect pests: As a single male may mate with a larger (often by orders of magnitude) number of females during its lifespan than vice versa, even highly efficient decimation of the males is unlikely to result in effective control of the pests, since the reproduction rate of the population is essentially determined by the number of fertile females available (recent studies have shown that in some species actually destruction of up to 99% of the males of an insect pest population may not affect the population's reproductive capacity significantly). However, females are generally not attracted by the pheromones of their own species, and thus they cannot be expected to be killed by pheromone-baited traps. Thus, it is generally acknowledged that “male annihilation” feasible using the “attract and kill” strategy is unsuitable for suppressing large pest populations unless combined with other approaches—which again reduces the specific benefits of the use of pheromone-baited traps.
Furthermore, the number of pest individuals present in any given environment is usually large enough, in particular when the pest is abundant enough to be an economically significant pest, to result in swift filling up and clogging of pheromone-baited traps, preventing contact of further visiting pests with the contact pesticide, thereby effectively rendering useless the traps. Given that for efficient control a large number of traps has to be dispersed over a considerable area (depending on the target pest and the attractant available, it is recommended to set up the traps at average distances amounting to no more than 10 m-25 m from each other for highly mobile insect pests), manually clearing out the traps is not efficiently feasible, in particular as this generally requires laborious operations including soap and water. Moreover, many pests are thought to be capable of emitting a “panic signal” (e. g. particular pheromones) upon distress, thereby warning others and potentially reducing the efficacy of the bait when allowed to remain in the trap for too long. The prolonged presence of dead pests within the trap is also prone to attract non-target organisms (Uchida et al., Proc. Hawaiian Entomol. Soc. 36: 135-143, 2003), which are then liable to exposure to very high dosages of the contact pesticide employed. This is particularly undesirable as natural predators for the target pests will suffer particularly, up to the degree that the controlling effects of the system are abolished by an ensuing lack of natural predators.